A generic stoichiometric equation for microalgae–microorganism nexus by using clarified domestic wastewater as growth medium

Abstract

Stoichiometric equations for microalgae–microorganism nexus culture were established by using 18 sets of experimental data from the literature where clarified domestic wastewater (CDWW) was used as a growth media. The best correlations between observed and calculated coefficients in the equations were 0.908, 0.878, 0.838, and 0.849 for reactors R₁, R₂, R_3, and the sum of three reactors, respectively. Then, each stoichiometric equation was generalized to quantitatively describe the reactions in each set of data for 18 different experimental conditions. By analysis, the most and second most sensitive limiting parameters were identified from the 18 stoichiometric equations. The formulas and equations were further upgraded to a generic form for a general organic growth medium (C_aH_bO_cN_dP_f). Microalgae–microorganism nexus was established by using the developed coefficients to depict the limited and balanced reactions. The study showed that nitrogen and phosphorus are required as additives in CDWW in order to gain a balanced microalgae–microorganism nexus for a higher yield of microalgae and microorganisms. For a balanced microalgae–microorganism nexus, the optimal nutritional molar ratio of C, N, and P in the CDWW growth medium was found to be 53:15:1.

Keywords:

• Microalgae
• Microorganism
• Nitrogen
• Phosphorous
• Stoichiometric

Acknowledgments

This project was supported in part by the Office of Naval Research (ONR) from the USA (Contract # N00014-08-1-0304) by Tier I: Reclamation Cooperative Agreement Program through Bureau of Reclamation GR0002841-GHASSEMI BOR COOP by the NSF Engineering Research Center: RenuWIT, and by the Ed & Harold Foreman Endowed Chair. We also thank anonymous reviewers and the editor from DWT for their constructive professional comments and advice.